The present invention relates to an inverter unit.
There exists a control unit for rotating electrical machines (a motor and generator) included in a drive unit that is used in an electric vehicle, hybrid vehicle or the like. An inverter unit as the control unit includes an inverter that controls such rotating electrical machines has been developed in recent years. Such an inverter unit may be structured such that a voltage boost circuit for boosting a power supply voltage is included to increase the outputs of the rotating electrical machines during high speed rotation thereof (for example, as described in Japanese Patent Application Publication No. JP-A-2007-89258 (Pages 11 to 12 and FIGS. 2 and 6)).
In the inverter unit, a reactor and switching elements for voltage boosting, which form the voltage boost circuit, are heat generating components as well as switching elements for the inverter that form inverter circuits that need to be properly cooled. The inverter unit disclosed in JP-A-2007-89258, therefore, includes a cooling plate with a coolant provided therein. The inverter unit has a structure for cooling the components forming the circuits such that the switching elements and a capacitor for voltage boosting are disposed to be in contact with one side of the cooling plate, and the reactor and capacitor for smoothing are disposed to be in contact with the other side thereof.
The above inverter unit is structured such that a coolant passage in the cooling plate is guided almost in a U shape inside the cooling plate. In other words, the coolant passage in the cooling plate has an outbound passage for cooling one half of the cooling plate and an inbound passage for cooling the other half thereof in the width direction thereof (hereinafter referred to as “the width direction”). The coolant flowing into the cooling plate flows in the outbound passage from one side to the other in the longitudinal direction of the cooling plate, turns there, and flows in the inbound passage back to the one side in the longitudinal direction. With regard to the reactor and switching elements that generate most of the heat of the circuit components, the reactor is disposed on the one side in the longitudinal direction of the cooling plate, and the switching elements are disposed on the other side in the longitudinal direction of the cooling plate. In other words, the reactor is disposed closer to the side on which the inlet and outlet of the coolant passage are provided, compared to the switching elements.